Leevell Peoples told The Associated Press on Wednesday her son Isaiah Peoples is a "model citizen'' and would not deliberately drive his car into pedestrians.

Authorities investigating the crash said Thursday that it remains unclear why Peoples crashed into the crowd Tuesday night. Sunnyvale Department of Public Safety Chief Phan Ngo added that Peoples "has not shown any remorse."

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Police said that Peoples, 34, a Sunnyvale resident, was being held on eight counts of attempted murder. Four of the victims remain hospitalized with major injuries, including a 13-year-old girl in critical condition.

Leevell Peoples said the only situation she can imagine could have influenced her son is a bout of PTSD. Leevell Peoples said Isaiah was an Army sharpshooter in Iraq but was discharged because of his PTSD. She added he had "a bad episode'' with PTSD about two years ago.

Peoples' grandmother confirmed to NBC Bay Area that he fought in Afghanistan and spent a year in a hospital for PTSD.

The crash was reported at 6:40 p.m. at the intersection of El Camino Real and Sunnyvale Saratoga Road, which is located near a number of restaurants and other businesses.

Before the crash occurred, Peoples had picked up food and was on his way to deliver it to his Bible study group, Ngo said Thursday.

Sunnyvale Department of Public Safety Capt. Jim Choi late Tuesday said police were investigating the incident as an intentional act due to initial statements made at the scene.

Ngo reiterated that stance Thursday, saying, "The evidence that we have, the physical evidence, and statements from witnesses led us to believe that it was a deliberate act by the suspect."

Authorities have said that the crash does not appear to have any ties to terrorism.

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FBI agents and police were seen Wednesday afternoon searching Peoples' residence in Sunnyvale.

Authorities have determined that Peoples had no criminal history prior to the crash. He has two Facebook accounts, but "nothing of significance" has been found on those accounts.

Peoples also possessed one weapon, which was described by Ngo as a "disassembled and inoperable" shotgun. The shotgun was found in the trunk of his car.

The car involved in the collision is registered to Peoples, according to the Department of Motor Vehicles.

An IHOP receipt recovered from the site of the crash shows the name of an Isaiah Peoples who used a Visa card to pay for his purchase on April 13.

Personal information on what appears to be Peoples' Facebook page, but wasn't confirmed by NBC Bay Area, shows he went to school at California State University, Sacramento.

Victims' belongings and bicycles lined the path the car took before the driver crashed into a tree.

A man who witnessed the crash said when he approached the driver's side of the car, the man was repeatedly saying, "thank you Jesus.''

Don Draper, of San Jose, said he was enraged after seeing the Toyota Corolla slam into pedestrians at high speed, then crash into a tree. He said he marched up to the car ready to confront the driver.

Draper said the driver was crouched over the steering wheel, unhurt. The car was hissing steam and the airbag had deployed.

Draper said the driver's speech was not slurred and he did not look at him.

Later, he saw the driver had climbed out of his car and was lying face down on the grass outside.